NAME
boolean - Boolean support for Perl
SYNOPSIS
use boolean;
do &always if true;
do &never if false;
do &maybe if boolean($value)->isTrue;
and:
use boolean ':all';
$guess = int(rand(2)) % 2 ? true : false;
do &something if isTrue($guess);
do &something_else if isFalse($guess);
and:
use boolean -truth;
die unless ref(42 == 42) eq 'boolean';
die unless ("foo" =~ /bar/) eq '0';
DESCRIPTION
Most programming languages have a native "Boolean" data type. Perl does
not.
Perl has a simple and well known Truth System. The following scalar
values are false:
$false1 = undef;
$false2 = 0;
$false3 = 0.0;
$false4 = '';
$false5 = '0';
Every other scalar value is true.
This module provides basic Boolean support, by defining two special
objects: "true" and "false".
RATIONALE
When sharing data between programming languages, it is important to
support the same group of basic types. In Perlish programming languages,
these types include: Hash, Array, String, Number, Null and Boolean. Perl
lacks native Boolean support.
Data interchange modules like YAML and JSON can now "use boolean" to
encode/decode/roundtrip Boolean values.
FUNCTIONS
This module defines the following functions:
true
This function returns a scalar value which will evaluate to true.
The value is a singleton object, meaning there is only one "true"
value in a Perl process at any time. You can check to see whether
the value is the "true" object with the isTrue function described
below.
false
This function returns a scalar value which will evaluate to false.
The value is a singleton object, meaning there is only one "false"
value in a Perl process at any time. You can check to see whether
the value is the "false" object with the isFalse function described
below.
boolean($scalar)
Casts the scalar value to a boolean value. If $scalar is true, it
returns "boolean::true", otherwise it returns "boolean::false".
isTrue($scalar)
Returns "boolean::true" if the scalar passed to it is the
"boolean::true" object. Returns "boolean::false" otherwise.
isFalse($scalar)
Returns "boolean::true" if the scalar passed to it is the
"boolean::false" object. Returns "boolean::false" otherwise.
isBoolean($scalar)
Returns "boolean::true" if the scalar passed to it is the
"boolean::true" or "boolean::false" object. Returns "boolean::false"
otherwise.
METHODS
Since true and false return objects, you can call methods on them.
$boolean->isTrue
Same as isTrue($boolean).
$boolean->isFalse
Same as isFalse($boolean).
USE OPTIONS
By default this module exports the "true", "false" and "boolean"
functions.
The module also defines these export tags:
:all
Exports "true", "false", "boolean", "isTrue", "isFalse", "isBoolean"
-truth
You can specify the "-truth" option to override truth operators to
return "boolean" values.
use boolean -truth;
print ref("hello" eq "world"), "\n";
Prints:
boolean
"-truth" can be used with the other import options.
AUTHOR
Ingy döt Net
COPYRIGHT
Copyright (c) 2007, 2008, 2010, 2011. Ingy döt Net.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
See http://www.perl.com/perl/misc/Artistic.html